The invention relates to a sanitary insert unit, having an insert housing in which there are formed a first flow path and a second flow path, wherein the first flow path and the second flow path extend in each case between at least one inflow-side inlet opening and one outflow-side outlet end, and having a valve body which can be adjusted from a first switching state to a second switching state counter to a return force, wherein the second flow path is closed by the valve body in the first switching state and is open in the second switching state.
Insert units of this kind are known and have proven useful, for example in water fittings, for switching between a first jet emerging from the first flow path and a second jet emerging from the second flow path. The known solutions involve switching off or interrupting the first flow path while switching on or opening the second flow path, such that, in each switching state, only one flow path is opened, and the respective other flow path is closed.
A sanitary insert unit of the aforementioned type with an insert housing has previously been described in U.S. Pat. No. 7,431,224 B2, in which insert housing a first and a second flow path are formed. The invention previously described in U.S. Pat. No. 7,431,224 B2 proceeds from prior art in which, in the fitting outlet, an insert is provided which is intended to assist in the uniform distribution of the emerging flow across the cross-sectional area and, if appropriate, also to ensure a uniform distribution of hot and cold water, so as to minimize the risk of the user scalding his hands when the stream of hot water is not mixed correctly with the stream of cold water. The prior art cited in U.S. Pat. No. 7,431,224 B2 generally takes the form of a transverse plug which can be fitted in the outlet orifice and which has a plurality of axial bores running through it. The combined cross-sectional area of the bores is generally slightly smaller than the cross-sectional area that is needed to accommodate the full flow rate of water through the valve mechanism, such that the transverse plug causes a slight backpressure at the tap outlet in order to create a jet of water from the tap. However, when the tap valve is only partially opened, the combined cross-sectional area of the bores in the plug exceeds the cross-sectional area needed to accommodate the full flow rate of water through the plug. The water then issues from the tap outlet as a slow flow of water due to the lack of pressure drop across the plug. Since the slow flow of water does not fill the outlet orifice but instead issues as a shallow flow over an arc at the lower portion of the plug, the shallow flow of water not only gives the appearance of a slow rate of flow of the water, but is also esthetically unacceptable to the user since the flow is in the form of a sluggish dribble from the tap. In order to create an insert unit which responds to the flow or the pressure and which controls the outflow of water such that the water emerges in an arrangement of jets with low flow rates, but when necessary also permits the complete flow of water, it is proposed in U.S. Pat. No. 7,431,224 B2 that the inlet in the insert housing is connected to the outlet via a first flow path and a second flow path, wherein a valve is provided in the second flow path and frees the second flow path when the water pressure exceeds a threshold value. The emerging water therefore initially flows at a low water pressure through a first flow path arranged in a ring shape and, after a threshold value has been exceeded and the valve in the second flow path has been opened, the water is also allowed to emerge through the second flow path lying to the inside.